CVE-2014-1558: Mozilla Firefox before 31.0 and Thunderbird before 31.0 allow remote attackers to cause a denial of service...

Security readout for executives and security teams

This is an old Mozilla Firefox and Thunderbird denial-of-service issue. A remote attacker could use a specially crafted X.509 certificate with unexpected character encoding to disrupt certificate parsing. The sources identify affected versions as Firefox before 31.0 and Thunderbird before 31.0. Exposure is most likely on legacy systems still running Firefox or Thunderbird before version 31.0. Modern managed endpoints are unlikely to be affected unless old browser or mail-client builds remain in embedded, kiosk, VDI, or unsupported desktop images. Address during legacy software cleanup unless affected old Mozilla clients are still internet-facing or business-critical. The issue is remote but limited to denial of service based on the provided sources. Mitigation focus: Upgrade Firefox and Thunderbird to version 31.0 or later.; Retire unsupported Mozilla browser and mail-client builds.; Check Mozilla and distribution advisories for current vendor guidance..

Prepared

Jun 14, 2026, 07:14 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.